1. Field of the Invention
The present invention relates to an image capturing apparatus, an angle-of-view adjusting method and a recording medium.
2. Description of the Related Art
A technology is known in which zoom magnification automatically controlled based on changes in the size of a subject. For example, a camera described in Japanese Patent Application Laid-Open (Kokai) Publication No. 2007-208453 applies a technology in which a moving subject is continuously detected and tracked by a template matching method, and zoom magnification is automatically controlled based on the changes in the size of the subject. As a result, a photographer can image a subject at an optimal size without performing a zooming operation.
However, the template matching method described in Japanese Laid-Open Patent Publication No. 2007-208453 has a problem in that the subject cannot be tracked when the size or shape of the subject being tracked changes significantly. In other words, in the template matching method, a current frame image is searched for a small image area similar to a template cut out from a preceding frame image (an image including the subject to be tracked), and an image area having the highest similarity is tracked as the subject. However, in a method such as this, when the size or shape of the subject changes significantly, the degree of similarity with the template cut out from the preceding frame image decreases and the subject cannot be tracked.
Therefore, for example, when a runner (a moving subject) approaches a camera from a distance, cuts across in front of the camera, and moves away from the camera, the template used for matching is required to be quickly and repeatedly updated, causing a problem in which the amount of processing required increases.